1. Field of the Invention
The present invention relates to a hydraulic apparatus for operating a clutch of a vehicle, particularly a tractor.
2. Description of the Related Art
A vehicle such as a tractor has a clutch operating apparatus for operating a main clutch interposed between an engine output shaft and a propeller shaft. This clutch operating apparatus may be a mechanical apparatus or a hydraulic apparatus, the latter including a master cylinder operable by a clutch pedal.
The hydraulic clutch operating apparatus includes an annular piston chamber concentric with the propeller shaft and defined adjacent a stationary supporting wall surrounding the propeller shaft. The piston chamber has an annular piston axially slidably mounted therein. The piston includes a bearing support at a forward end thereof for supporting a release bearing. When the clutch pedal is depressed, pressure oil is supplied from the master cylinder to the piston chamber to slide the piston. As a result, the release bearing pushes release elements to disengage the clutch.
Conventionally, the piston and bearing support are formed integral with each other, and the piston is mounted in the piston chamber with appropriate inner and outer spaces therebetween. These inner and outer spaces are sealed by oil seals.
Where the release elements of the clutch are the lever type, a plurality of release levers are arranged circumferentially. The release bearing pushes inward ends of the release levers to produce a half-clutch state or declutched state.
However, it is extremely difficult due to variations occurring during manufacture and for other reasons to arrange all of the inward ends of the release levers in the same plane or axially flush with one another. Consequently, when in a half-clutch state, one or more of the plurality of release levers may remain out of contact with the release bearing, thereby to produce an uneven contact state.
In such an uneven contact state, the release bearing tends to make an eccentric movement instead of smoothly rotating about the axis of the propeller shaft. Such movement of the release bearing is transmitted through the bearing support to the piston. As a result, the piston makes an unsteady axial movement in the cylinder chamber to cause pressure variations. In a half-clutch state, oil leakage could also occur due to wear or damage of the oil seals.
To avoid direct transmission from the bearing support to the piston of displacement due to the eccentric movement, the bearing support and piston may simply be divided as disclosed in U.S. Pat. Nos. 4,684,003 and 4,660,702. Although vibrations transmitted directly through solids may be stopped at the dividing point, this construction is insufficient for suppressing vibratory shocks due to the eccentric movement of the release bearing, and for allowing steady sliding movement of the bearing support.